1. Field of the Invention
The present invention relates to a structurally tuned, vibration based component checking system and method for detecting component anomalies in an assembly prior, to the component being installed in the assembly.
2. Background Art
With ever increasing emphasis on quiet vehicle rides, the noise, vibration and harshness (NVH) levels in vehicle powertrains have assumed a significant role in defining the overall noise levels in a vehicle. For example, gear noise can be a major contributor to unacceptable transmission NVH levels which, in turn, contributes to unacceptable NVH levels in vehicles. To deal with these issues, a variety of gear measurement and checking systems have been developed to identify and eliminate noisy gears before they are assembled in transmissions and installed in a vehicle.
Current practice also includes placing test stands in transmission manufacturing plants to check NVH levels after the transmissions are assembled. Computer aided simulations of transmissions, and even complete vehicle dynamics, are also used. This is complemented by vehicle road tests for a certain number of transmissions manufactured and assembled.
Although these testing procedures after transmission assembly may reduce the number of noisy transmissions installed in vehicles, detecting unacceptable NVH levels at an end-of-line test stand, or by road tests, is costly and wasteful. Therefore, different gauging/checking strategies are available for detection of gear defects before assembly at machining departments. The current gauges in place in machining areas have limited detection capabilities; and often do not detect subtle gear anomalies which can lead to unacceptable NVH levels in a vehicle.
The gear gauging systems currently available in machining departments measure dimensional features of the gears and the tooth surface profiles. They are, however, not capable of performing functionality based NVH checking of the gears before they are used in a transmission assembly. Furthermore, there are a few other types of gauging systems in place, including Transmission Error (TE) testers and testers which measure vibration characteristics. These also have limited capabilities.
One limitation in these systems is that the dynamic response of their structures do not correlate in any way with the structural response of the fully assembled transmission systems. Therefore, they fail to detect the micron level subtle anomalies which would produce noise in the assembled transmission. In such a system, the structural components may be generally very stiff, resulting in low excitation levels in response to gear defects. Thus, by attempting to reduce the vibration of the gear checking structure, the checking structure no longer resembles the finished assembly, and the test results may not be indicative of how the tested component will perform when it is installed.
Therefore, a need exists for a component checking system and method capable of detecting subtle anomalies in a component of an assembly, prior to the component being installed in the assembly.